PeachParts Mercedes-Benz Forum - View Single Post - Looking for any performance tips for my 300D

rwthomas1 · #8 10-06-2003, 11:10 PM

Hey Cumminsnut,
All good info so far. You will find there is a "keep it stock" or "MB knows best" mentality around this board, for better or for worse. The MB is similar to Ford 7.3 IDI (pre powerstroke) and the GM 6.2-6.5 diesel engines in head/prechamber design. Any mods that work on them should work on an MB. The MB's have a high 21:1 compression ratio, like the GM's. Since the GM's don't tolerate more than 15psi without intercooling when using stock pistons I would say this is likely the limit with the MB as well. There is a boost switch on MB's that cuts fuel if boost goes beyond 1.1 bar (about 15psi) hooked into the ALDA boost reference line so I would think this is an indication from MB not to go higher. The wastegate is adjustable and there are a few posts on how to perform this so do a search. Regarding EGT's since you mess with modded truck diesels you should be aware the maximum pre-turbo EGT on most engines is 1350-1400* I would shoot for 1250* preturbo or 1000* post turbo as a maximum. Nobody here likes to run egt/boost gauges either. Trusting instead that ultra-accurate "viewing smoke in rearview mirror" method when they tweak the ALDA. I think egt/boost gauges are a better option...... Since you have the engine apart now is the time to do a little pocket porting, gasket matching, etc. A little flow gain here an there could add up to a lot. Everyone here will tell you a free-flowing exhaust isn't worth it. Since nobody has proven it won't work and if you mess with trucks you know thats one of the first mods done, I say go for it. Sure can't hurt. Welcome and enjoy! RT